It was a greeting fit for royalty, too, as the Mets officially unveiled Johan Santana with a glitzy, made-for-TV ceremony at Shea Stadium that was held in two languages and came complete with celebrity tributes ranging from Mayor Bloomberg to Jerry Seinfield.

Last September’s epic collapse suddenly seemed like ancient history – or so the Mets hoped.

“This is an historic day for the Mets franchise,” general manager Omar Minaya beamed to the overflow crowd of reporters.

At least for the moment, the only keys the Mets didn’t hand their new $137.5 million ace yesterday was the top spot in their rotation. Treading lightly with Pedro Martinez’s feelings, manager Willie Randolph said the decision between starting Martinez or Santana on Opening Day wouldn’t be made until spring training.

“I have two legitimate stoppers, so I have a choice to make,” Randolph said. “But I’m sure it will be a pleasant choice. I’ve got a month to think about that.”

Randolph has had the chance to enjoy that tantalizing dilemma since last Friday night, when the Mets finally completed their blockbuster trade with the Twins by giving the two-time Cy Young winner the largest contract ever for a pitcher. The proceeding five days were a whirlwind for Santana, although the Venezuelan left-hander appeared to handle yesterday’s New York-sized introduction as nimbly and confidently as he does opposing hitters.

Accompanied by his father, Jesus, and wife, Yasmile, Santana was besieged by questions about switching to the National League and how he would handle the suffocating expectations that come with playing in the country’s largest market. Santana admitted the New York microscope would be “an adjustment,” although he deftly tried winning the local fans over by saying he had watched the Giants’ Super Bowl victory parade on Tuesday.

“I’m looking for the Mets to celebrate that way, too,” Santana said. “Hopefully, that time will be soon and we’ll be able to bring that kind of happiness to the city, too.”

Another admittedly major adjustment for Santana will be playing in the NL without the aid of a designated hitter. “It’s going to be a challenge, because I have to learn how to hit and run the bases,” he said. “I know how to pitch, but playing in the NL goes beyond pitching.”

Not that the Mets are worried about Santana’s hitting skills. Not only did Santana start his career as an outfielder, but he roped a double against them amid a complete-game win at Shea last summer. Santana also is a .258 hitter in 31 career interleague at-bats.

“I’m not going to pull a Tony La Russa and hit him eighth, but he has an idea of how to swing the bat,” Randolph said.

The Mets think the NL – its hitters, in particular – will have a tougher time adjusting to Santana than the other way around. AL hitters, after all, rarely got a handle on Santana’s wicked fastball-changeup combination in his eight seasons in Minnesota, when he rang up a whopping 1,381strikeouts.

“He just needs to do what he’s been doing,” Randolph said. “I don’t want him to get away from who he is. He needs to dictate.”

The Mets don’t have any worries about Santana- who turns 29 next month – imposing his will on the NL. The bigger concern until last Friday was simply getting Santana in a Mets uniform. Talks nearly broke down Friday night over the size and length of the record-setting contract, and Santana said yesterday he was prepared to return to the Twins and pitch the final season of his contract if it hadn’t gotten done.

But Santana, who found out about the trade while at his home in Fort Myers, Fla., sounded as if being a Met was what he wanted all along – despite months of rumors about heavy interest from the Yankees and Red Sox.

“I told [agent Peter Greenberg] that I wanted to experience something different,” Santana said. “When it was getting close, I told him I liked the idea of going to the Mets. I knew people there. That’s when I said, ‘OK, I hope it’ll be the Mets. Peter, do your job and get this done.'”

Greenberg got it done, making the Mets feel like instant NL favorites in the process. “It gives you a little swagger,” Randolph said. “We felt good going into spring training as it was, but when you add a guy of Santana’s caliber, you definitely have a little more swagger.”